Islamabad , Pakistan -LRB- CNN -RRB- -- Police in the Pakistani city of Karachi have opened a murder case against the owner of a garment factory where a fire killed more than 250 people this week , a senior police official said Thursday .

Also under investigation are the two sons of the factory owner , whose name is Abdul Aziz ; the managers of the factory ; the shareholders of the factory ; and any government official who failed to enforce safety regulations at the factory , said Amir Farooqi , a senior Karachi police official .

The announcement means police officers will investigate the fire -- one of the worst industrial accidents in Pakistan 's history -- gather evidence and submit their findings to prosecutors who will then decide whether to charge the individuals .

Farooqi said police have opened a murder case because the exit doors of this factory were locked , preventing many people from escaping the blaze that swept through the building during Tuesday night and continued to burn Wednesday .

Nobody has been arrested in the case yet . Police officers are still looking for Aziz and his sons , who are believed to be `` hiding , '' Farooqi said .

Other charges in the case may eventually include causing bodily harm , negligence and destruction of property , he added .

At this phase in the investigation , police do not have to name all of the accused . That 's why they 're not identifying any government officials or factory managers at this point .

Earlier Thursday , Karachi authorities lowered the death toll from the blaze to 258 from 289 previously .

The higher toll reported Wednesday became inaccurate because of the rapidly rising number of deaths and confusion amid multiple rescue and recovery operations , according to Karachi Fire Department Chief Ehtesham Salim and Shabih Saddiqi , a local government official .

Salim said the latest death toll is based on the number of bodies and remains recovered from the factory .

Several people are still missing and recovery crews are working to find them .

Salim said investigators are still trying to establish what caused the fire .

Journalist Nasir Habib contributed to this report .

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Karachi authorities lower the death toll from the fire to 258 from 289

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Police open a murder case against the owner of the factory and others

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The locked doors of the factory prevented people from escaping , police say